1. Field of the Invention
The present invention relates to a mobile robot, and particularly, to an apparatus and a method for correcting a position of a mobile robot.
2. Description of the Background Art
In general, a mobile robot, particularly, a robot cleaner means a device for automatically cleaning an area to be cleaned by sucking foreign substances such as dust or the like from a floor while moving along a wall surface of a room of a house (e.g., living room, inner room or the like) by itself without any manipulation of a user.
The robot cleaner determines a distance between itself and an obstacle such as furniture, office supplies, wall or the like installed in an area to be cleaned through a distance sensor. According to the determined distance, the robot cleaner selectively drives a motor for driving its left wheel and a motor for driving its right wheel, thereby switching its direction by itself and cleaning a cleaning area. Here, the robot cleaner performs a cleaning operation, moving in the cleaning area through map information stored at an internal storing unit.
Hereinafter, mapping for generating the map information will now be described.
First, the robot cleaner moves along a side surface of an operation space (e.g., a wall surface of a living room of a house), to calculate a distance and a direction from itself to a charging station installed at a wall, and scans an operation space, determining its position on the basis of the calculated distance value and direction value. Here, the robot cleaner detects its current position by using an encoder installed at its wheel.
The robot cleaner determines whether there is an obstacle between itself and the charging station. If there is no obstacle, the robot cleaner scans an operation space by transmitting/receiving a signal to/from the charging station. On the other hand, if there is an obstacle between the robot cleaner and the charging station, the robot cleaner scans another operation space, first. Then, when the obstacle is gone, the robot cleaner scans the operation space where the obstacle has been gone, transmitting/receiving a signal to/from the charging station.
However, the method for detecting a position of the robot cleaner by using the encoder has a problem that an error is generated because of sliding of the wheel or idle rotation since a current position of the robot cleaner is searched by using the encoder installed at its wheel.
In a method for detecting a position of a robot cleaner in accordance with a different conventional art, stickers or reflection plates having the same shape are installed in an operation area (e.g., a wall surface of a living room of a house) at prescribed intervals, and the robot cleaner recognizes the stickers or the reflection plates by using a CCD camera to thereby correct an error generated by the sliding of the wheel and the idle rotation and thus recognizes a distance between itself and a charging station. However, the method for detecting the position of the robot cleaner by using the sticker or the reflection plate has a problem that a distance error is accumulated when illumination brightness of a cleaning operation area is changed, or a subject having a shape similar to the sticker or the reflection plate is recognized.
In addition, if the illumination brightness becomes lower or higher than a threshold, the robot cleaner cannot check its position since a CCD (charge-coupled device) camera cannot recognize the sticker or the reflection plate. Also, since the CCD camera has to be installed at the robot cleaner, a fabrication cost of the robot cleaner is increased.
Technologies about a robot cleaner in accordance with a conventional art are disclosed in U.S. Pat. No. 5,440,216 and No. 5,646,494, which have been issued.